In article ,
Mark Roberts wrote:

Is the HD compression scheme one that allocates a fixed number of
bits to each channel, regardless of the need for those bits at any
moment in time?

Yes.

One also questions the wisdom of further compromising audio quality
on a station that's all-news. The HD compression scheme really
chews up voices but can be somewhat more tolerable on music. (I
readily admit this statement is a matter of perception.)

This is why AM talkers are dropping "HD", at least the ones who take any
pride in their sound. KGO dropped it for two reasons: it made them sound
much worse, and it interfered with other stations on the west coast at
night. The proprietary iBiquity codec is not friendly to voice at low
bit rates at all.

It also appears that, at least in the San Francisco Bay Area, CBS
is being most aggressive with its HD programming. If there will be
an HD-3 channel for KFRC-FM, it will be the second station in the
Bay Area with one. The other is KCBS's KITS, running alternative on
the main channel, "classic alternative" on HD-2, and the last.fm
"discovery" channel in mono on HD-3.

There isn't much to be lost there. Both of those stations (particularly
KITS) sound pretty bad in general. CBS seems to have developed an
extremely aggressive stance when it comes to IBOC. While others have
abandoned digital on AM, CBS still hangs in there.

None of the other stations
with HD are running a third channel. From a visit to New York City
last year, I recall that use of HD-3 is more widespread there.

I can see that. During my visits there I note that radio in general
sounds like trash, so the effects of tinier and tinier bit streams are
probably taken in stride by the listeners.

--
John Higdon
+1 408 ANdrews 6-4400
AT&T-Free At Last